2 14 POPULAR SCIENCE MONTHLY. 



data of mosasaurs and has added four new genera. Baur gave tlie 

 first complete description of the skull of a species of Platecarpus. 

 Williston and Case first described the vertebral column and extremi- 

 ties and the general form of mosasaurs. The former has contributed 

 most to our knowledge of mosasaurs in the Kansas Cretaceous, and 

 made the first correct restoration, which is made one of the bases of 

 this paper. 



Professor S. W. Williston, University of Kansas, because of his 

 ])erfected restorations and wide studies of the sea-serpentlike saurians, 

 the mosasaurs and other marine saurians, must rank as the highest 



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1>- 





A-. 





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Fragment of Scaled Skin of Mosasaurs. Natural size. 



authority-. It is largely on his nuiterial that it is possible to present 

 something like a complete view of the gigantic monsters that sw^am 

 the Cretaceous seas and gave origin to our notions of mythical sea 

 serpents. Kansas is the great center of the Cretaceous time of occu- 

 pation, and it is within its borders that the largest number of species 

 and genera of sea serpents have been discovered. It is natural, per- 

 haps, that living in the vicinity of the most prolific Cretaceous re- 

 mains, Professor Williston should be better able than scientists more 

 remote to complete our knowledge of marine saurians. 



There are three groups of the serpentlike sea saurians — the 

 ichthyosaurs, plesiosaurs, and mosasaurs. Of the mosasaurs, Kansas 

 has produced the largest number of species, twelve of which have been 

 satisfactorily described. JSTew Jersey, Alabama, Carolina, and Mis- 

 sissippi have perhaps ten valid s]:)ecies. Dakota has favored us with 

 three species. It is estimated that of fifty species attributed to ISTorth 

 America, about twenty-five or thirty will be distinguished as dis- 



